Plant for producing a fibre web of plastic and cellulose fibres

ABSTRACT

A plant serves as a mean for production of a fibre web of synthetic fibres, such as plastic fibres and absorbent fibres, such as viscose and cellulose fibres. The plant includes a forming head preliminary to lay a homogeneously and smoothly distributed fibre layer on a net shaped wire. Furthermore the plant includes a hydro-entangling section with liquid nozzles with powerful liquid jets to treat the in the forming head formed fibre layer, which consists of both synthetic—and absorbent fibres. The plant also includes an oven subsequently to thermal bond the synthetic fibres with cross bonds in the affected areas. Finally the dried web is winded up in a roller. By the help of the plant according to the invention, by higher production speed than known previously a fibre web can be produced, which is far cheaper, and which has a better and more homogeneous structure than similar conventional fibre webs.

BACKGROUND ART

The invention concerns in any case synthetic fibres, such as plasticfibres and absorbent fibres, such as viscose and cellulose fibres toproduce a fibre web, which at least include one heat-treatment sectionfor heating up the synthetic fibres at least to one in advancedetermined temperature, and at least one hydro-entangling section withliquid nozzles to aim a number of powerful liquid jets against one madeof synthetic fibres and absorbent fibres combined fibre layer.

A such plant is known, where long, carded, synthetic fibres of forinstance polypropylene or polyethylene are laid in a web shaped layer onthe top side of a net shaped, endless wire's upper tissue, which whilerunning simultaneously runs in a direction, which points towards theplant's outlet. On the same or on a following wire the fibre layerhereafter is guided through an oven, where the fibres are heated up tosuch a high temperature that they will be tied together with cross bondsin the affected areas.

A thermal bonding fibre layer has now been formed, serving as aframework and supporting web for absorbent fibres, such as viscoseand/or cellulose fibres, which as web can be un-winded from a roller orapplied in an air-flow with the help of a known forming head.

A close-meshed wire transports hereafter the supporting web with theapplicated fibres through a battery of water nozzles, which send apowerful water jets down against the fibres, which hereby are driveneffectively into the underlying, frame-like supporting web.

When the water jets touch the close-meshed wire, part of the water ishit back against the supporting web, with the help of which theapplicated fibres are wound around the cross bonded, synthetic fibresand are laid closely against the web's lower side, which hereby will beconveyed a smooth and flush surface.

The mentioned water exposure is in technical terms calledhydro-entangling or spun-lacing. In the following the termhydro-entangling will be used.

The hydro-entangled web is dried in an oven, and finally the web iswound up in shape of a roller.

Fibre webs, which are manufactured in this way, are for instance usedfor products as wet wipes, towels, drapes, and gowns.

The above described process can be varied in several ways, which howeverhas in common that they all start with a carded fibre layer. Typicallythe layers will be of polypropylene, polyethylene, or viscose, or amixture of such fibres.

The carded made supporting web is soft and suitable for absorbing andintimately connect with the applicated fibres. In the longitudinaldirection besides the web has such a matching strength that the processcan proceed without a large risk of web breakage, which could lead toexpensive stops of production and losses of materials.

Another advantage is that during the hydro-entangling process hydrogenbonds are made between the fibres, to avoid that the finished productflock and mote by use or processing.

The carding process however is slower than the following processes,which therefore cannot proceed with optimum capacity, this means theyield is reduced to a level, which is set by the carding process. Sinceplants of this kind are extremely expensive, it must be considered aserious lack that a great part of the known plant thus is not being usedto the full extent.

Besides the carding process requiring close supervision and control, andit is difficult and complicated to work with, because for instanceduring running it is necessary to stretch the carded fibre layer.

The synthetic fibres, which make up the supporting web are furthermoreconsiderably more expensive than cellulose fibres, and since the knownprocess requires that approximately equal size quantities are being usedof the two fibre types, the resulting product becomes expensive.

Even with the above mentioned content of synthetic fibres, the finishedfibre web anyhow will suffer from the main lack that there exists aneven big difference in the strength respectively in the longitudinal andtransverse direction. The strength scale is typically 5:1. Products,which are manufactured of such fibre webs, therefore may tend to partalongside during use. Thus it is easy to stick a finger through theproduct.

A further disadvantage is that the known plant due to the cardingprocess is rather unfit for production of sandwich webs, where thecarded fibres become a part of several layers. The known plant cantherefore not be used for production of one of today's strongly demandedproducts, which consists of two non-woven fibre layers with anintermediate air-laid fibre layer, which is tied together with the twoothers by the help of hydro-entangling layer, which is tied togetherwith the two others by the help of hydro-entangling.

SUMMARY OF THE INVENTION

The purpose of the invention is to assign a plan t of at the openingmentioned character, which has a simple and cheap structure, which iseasy to work with and financially favourable while running, and whichfurthermore can manufacture at a larger transition speed than known sofar.

Another purpose of the invention consists of assigning a plant of at theopening mentioned character, by means of which a fibre web with abalanced proportion between the strengths respectively in thelongitudinal and transverse direction can be manufactured.

A third purpose of the invention consists of assigning a plant of at theopening mentioned character, which is designed to manufacture fibre webstaking price and features into consideration for optimum proportionsbetween the quantities of fibre types used for manufacturing the web.

A fourth purpose of the invention consists of assigning a plant of atthe opening mentioned character, by means of which a fibre web can bemanufactured, which has a more homogeneous and precise distribution offibres than formerly known.

A fifth purpose of the invention consists of assigning a plant of at theopening mentioned character, by means of which a fibre web with tightertolerances than formerly known can be manufactured.

A sixth purpose of the invention consists of assigning a plant of at theopening mentioned character, by means of which a sandwich fibre webeasily can be manufactured.

The new and specific, by means of which this is achieved according tothe invention consist of the plant besides include an air-laying sectionincluding means during operation to generate a mainly verticaldescending air-flow through at any rate the upper tissue on a mainlyvertical running net shaped, endless wire, and successively supply theair-flow with at least synthetic fibres and distribute these in a smoothand homogenous, web shaped layer on the upper side of the wire's uppertissue, which under here runs in one against the plant's outlet pointingdirection.

When the known plant's carding process thus is replaced by a reliableand financially favourable air-laying process the plant's remainingequipment is now made able to operate at optimum production speed,simultaneously the process becomes easy to control. The fibres can bedistributed homogeneously and precisely with an equal orientation in alldirections, thus the finished fibre web achieves approximately samestrength in longitudinal and transverse direction, and besidesmanufacturing with tight tolerances becomes possible.

Now the process does not require a large strength in the longitudinaldirection anymore, and the expensive synthetic fibres can among otherthings for this reason to a large extent be replaced by cheapercellulose fibres, by means of which the finished fibre web's absorbentfeatures are improved favourably, and the cost price is being reduced.

It is especially favourable, when the absorbent fibres are added at thesame time as the synthetic fibres in the same air-laying section, sincethe fibres hereby are mixed intimately from start, and the supportingweb will be integrated in the forming process.

For the purpose a forming head can be used, which include a under thewire's upper tissue placed suction box, which is connected t o a vacuumair pump, one above the wire placed house with one or more fibre inlets,and one in the house above the wire placed number of rotary wings forwhile operating to distribute the fibres in a flush layer on the upperside of the wire's upper tissue.

A simple and cheap construction form for the plant can be constructed ofa forming head for at a time to form both the synthetic fibres and theabsorbent fibres, a hydro-entangling section, and an oven withsufficient high treatment-temperature to thermal bond the syntheticfibres in the affected areas.

By this construction the thermal bonding of the synthetic fibres takesplace in the same oven, which is used for drying the hydro-entangledfibre web. When a specific thermal bonding oven is inserted between theforming head and the hydro-entangling section, the process can becontrolled very precisely, because the temperatures in respectively thethermal bonding oven and the later drying oven can be adjusted to anoptimum for the respective processes. Furthermore the fibre web is nowstabilised, when it passes through the hydro-entangling process, whichtherefore can proceed with an optimum effect and without a large wasteof loose fibres.

When the single forming head in one of the two above mentionedconstruction forms for the plant according to the invention is replacedwith three on one-and-another following forming heads, the plant can besuccessfully used for production of sandwich fibre webs, since themiddle forming head then mainly is supplied with for instance cellulosefibres, while the two other forming heads are supplied with syntheticfibres or both synthetic fibres and cellulose fibres.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention regards also a fibre web, which is manufactured by thehelp of the above mentioned plant according to the invention, and whichcontains synthetic fibres as well as absorbent fibres. Due to theproduction process this web has a structure with a homogenousorientation of the fibres in all directions and a good balance betweenthe strengths respectively in longitudinal and transverse direction.

An effectively tied and therefore strong fibre web is achieved, when thesynthetic fibres are bi-component fibres, which each consists of a coreof at first plastic and then of another one of plastic with a highermelting point than the first. When this form of synthetic fibres arebeing used, bonding is secured in all places, where the fibres meet,without a simultaneous risk of the core to melt, by which the bondingfeature would be lost.

With the help of the plant according to the invention manufactured fibreweb can favourably have a percentage content of cellulose fibres ofbetween 50 and 95, mainly between 60 and 90, and especially between 75and 85, at which the web becomes substantially cheaper than theconventional fibre webs of this type.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically a first construction form for a plantaccording to the invention

FIG. 2 shows schematically a second construction form for a plantaccording to the invention.

FIG. 3 shows schematically a third construction form for a plantaccording to the invention, and

FIG. 4 shows schematically a fourth construction form for a plantaccording to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 a first construction form for a plant according to theinvention can be seen. The main components are a forming head 1, aconveyor 2, a hydro-entangling section 3, an oven 4, and a windersection 5.

The forming head 1 consists of a house 6 with a fibre inlet 7 forsynthetic fibres, for instance plastic fibres, and a fibre. inlet 8 forinstance cellulose fibres

Below the house a net shaped wire 9, having an upper tissue 10 and alower tissue 11 runs above roller 12.

Close under the wire's upper tissue 10 a suction box 13 is placed, whichis connected to a vacuum pump 14, and above the wire's upper tissue 10 anumber of rotating wings 15 are placed.

During operation the vacuum pump 14 provides via the suction box 13 andthe house 6 an air-flow, which from an unshown source for syntheticfibres and likewise an un-shown source for absorbent fibres, as forinstance cellulose fibres, leads synthetic fibres and absorbent fibresinto the house 6 via respectively the fibre inlet 7 and the fibre inlet8.

The air-flow flows down through the wire's upper tissue 10, while thefibres are kept back on the tissue's upper side, where those are mixedand distributed by the rotating wings 15 in an flush and homogeneousfibre layer 16 with a random and even orientation of the fibres in alldirections.

Simultaneously the wire runs 9's upper tissue 10 in the arrow showndirection against the plant's outlet at the winder section 5, anddelivers under here the fibre web 16 to the conveyor 2.

This conveyor 2 consists of a wire 17, which overlaps the forming head'swire 9 and runs over rollers 18. The wire 17 has a lower tissue, whichis placed on the upper side of the fibre layer 16.

The suction box 20, which is connected to a vacuum air pump 21 and isplaced above the wire 17's lower tissue, generates a negative pressure,which holds the fibre layer 16 on to the wire 17's lower tissue 19,which thereby will be able to transport the fibre layer 16 to thehydro-entangling section 3 in the with the arrow shown direction.

This hydro-entangling section 3 consists of a relatively close-meshedwire 22, which overlaps the wire 17 of the conveyor 2 and runs aboverollers 23. The wire 22 has an upper tissue 24, which is placed on thelower side of the fibre layer 16.

A number of water nozzles 25 are placed above upper tissue 24 of thewire 22, sending powerful water jets 26 down against the fibre layer 16,which are held to the web by an underlying suction box 27, which isconnected to a vacuum air pump 28. Water and loose fibres will beremoved from the suction box 27 by the pump 28.

The water jets wind the fibre web's different fibres together in astrong bond. A portion of the water fights at the meeting with theclose-meshed wire 22's upper tissue 24 besides back against the fibreweb's lower side, supplying a flush and smooth surface.

Furthermore the hydro-entangling treatment effects that between thefibres, hydrogen bonds will be formed, which prevent flocculation anddust by use and during processing.

After the hydro-entangling treatment, the now relatively strong and wellcoherent fibre web runs into an oven 4, which works at a sufficient hightemperature to thermal bond the synthetic fibres in the affected area.Simultaneously the web will be dried.

In the oven 4 a rotating roll 29 is equipped with a perforated wall,which allows a warm flow of air to pass. The air-flow will bere-circulated as shown by the help of fans 30.

During the passage of the oven 4 the fibre web 16 runs around rollers 31and the in arrow pointing direction rotating roll 29, by means of whichthe warm air will be forced through the fibre web, which dries,simultaneously a cross bond in the contact points will be formedmutually between the synthetic fibres and to a certain extent alsobetween the synthetic fibres and the absorbent fibres.

Finally the finished fibre web will be wound up into a roller of fibreweb 32 in the roller section 5, which fundamentally consists of a winder33 with a driven roller 34 and an idler roller 35.

FIG. 2 shows other construction form for a plant according to theinvention and separates itself from the above described and shown inFIG. 1 first construction form by, a special thermal bonding oven 36being inserted between the conveyor 2 and the hydro-entangling section3. Similar parts are therefore indicated with the same referencenumbers.

The thermal bonding oven 36 is a continuos oven, which the upper tissue37 passes through on a wire 38, which runs above roller 39. The fans 40serve the purpose of re-circulating the air across through the fibre web16 and the upper tissue 37 of the wire 38, which carries the fibre web.

The thermal bonding oven 40 works with a temperature, which issufficiently high to bond the synthetic fibres together in the affectedareas, however not that high that the fibres melt noticeably.

The process in the thermal bonding oven is easiest controlled, whenbi-component fibres are used. When the core for example has a meltingpoint of 180 Celsius and the shell a melting point of for example 135Celsius, the temperature in the oven must be kept in a spot betweenthese two temperatures to efficiently cross bond the synthetic fibres inthe affected areas without risking the core to melt simultaneously.

One of the advantages, which is obtained by using this special thermalbonding oven 36, consists of the fibre web 16 is stabilised in advance,thus the following hydro-entangling process can proceed with increasedcertainty and less fibre waste, which must be lead away in thewastewater.

Another advantage consists of the oven 4, now just needs to work as adrying oven, and therefore can work with a here fore fitted lowertemperature, which size furthermore is uncritical.

FIG. 3 shows third construction form for a plant according to theinvention and separates itself from the above described and shown inFIG. 1 first construction form by, instead of only one forming headthree exists placed after one-another 41, 42, and 43. Each of theseforming heads are constructed in the same way as the first constructionsform's forming head 1. Similar parts are therefore indicated with thesame reference numbers.

When the plant in this way is supplied with three forming heads, it canbe used for production of sandwich-fibre web, which typically consist ofa soft thermal bonded top- and bottom layer with an absorbent core. Thesandwich-fibre web can for example have following combination.

EXAMPLE 1 Bottom layer 15 GSM

The proportions between the synthetic fibres and the absorbent fibres,such as cellulose fibres 10-5. This means that 67% of the bottom layerconsists of synthetic fibres and 33% of absorbent fibres.

Middle layer 30 GSM

The proportions between the synthetic fibres and the absorbent fibres,such as cellulose fibres 3-27. This means that 10% of the middle layerconsists of synthetic fibres and 90% of absorbent fibres.

Top layer 15 GSM

The proportions between the synthetic fibres and the absorbent fibres,such as cellulose fibres 7-8. This means that 47% of the top layerconsists of synthetic fibres and 53% of absorbent fibres.

The process processes in a way that the first forming bead 41 will besupplied with the fibres for the bottom layer, the other forming head 42with the fibres for the middle layer, and the third forming head 43 withthe fibres for the top layer, thus the three layers will be formed ineach layer's separate forming head 41, 42, 43 and successively will belaid on top of one-another. Subsequently the process continues in thesame way as described for the first construction form.

The in FIG. 3 shown fourth construction form for a plant according tothe invention separates itself from the above mentioned and in FIG. 3shown third construction form by, now similar to the other constructionform, and as shown in FIG. 2, a special continuous thermal bonding oven36 is inserted between the conveyor and the hydro-entangling section 3.Similar parts are therefore also in this case indicated with the samereference numbers.

With this setting of the plant according to the fourth construction formthe same advantages will be achieved as described in connection with thedescription of the other construction form.

In the below table indicated data respectively for a card based productand a product according to the invention serves the purpose of makingthe advantages clear, which can be achieved by the invention.

EXAMPLE 2

Product Card based according to Product features product the inventionContent of thermal 50%  5%-45% bonding fibres Content of cellulose 50%95%-55% fibres Length of thermal 12-60 mm 2-25 mm bonding fibres Lengthof viscose 6-60 mm fibres Length of cellulose 0-6 mm 0-6 mm fibresLength of alternative 2-25 mm fibres (for example absorbent fibres) Drystrength, 100 N/50 mm *) 25-50 N/50 mm *) longitudinal direction Drystrength, 20 N/50 mm *) 15-30 N/50 mm *) transverse direction Wetstrength, 100 N/50 mm *) 19 N/50 mm *) longitudinal direction Wetstrength, 20 N/50 mm *) 11 N/50 mm *) transverse direction *) gramweight 65 g/sqm 65 g/sqm

As it can be seen, a great part of the expensive synthetic fibres in theconventional card based product has been replaced by cheaper cellulosefibres in the inventive product, which in this way can manufacture at afar lower price than the conventional product.

Simultaneously the inventive product's strength is favourable fairlyidentical in the longitudinal and transverse direction, while theconventional product's corresponding strength ratio is as 5-1.

It must be noted that the above described and on the drawing shownconstructions forms only serve as considerate examples of, how a plantaccording to the invention can be arranged.

In this way the plant can, within the frame of the invention'sprotection scale after need be supplied with two, four, or a biggernumber of forming heads, which besides do not necessarily need to beplaced in a row just after one-another.

Furthermore in the production line one or several further sections canbe inserted to in dependency of the wished quality to treat the fibreweb.

1. A plant for producing a nonwoven fabric at least of synthetic fibrescomprising: at least one air-laying station comprising: an endless wire,a suction box, which is connected to a vacuum pump, said suction boxbeing placed under said endless wire, a house with one or more fibreinlets, said house being placed above the upper part of said endlesswire, a number of rotatably arranged wings for during operationdistributing the fibres in a non-woven web upon the upper part of saidendless wire, said wings being placed above said endless wire in saidhouse, at least one heat-treatment station for bonding the syntheticfibres by heating the web, said heat-treatment station being arrangeddownstream of said at least one air-laying station, at least onehydro-entangling station for directing a number of powerful liquid jetsagainst the bonded web, said hydro-entangling station being arrangeddownstream of said at least one heat-treatment station, and means forcontinuous transport of the web through the plant.
 2. A plant accordingto claim 1 wherein at least one drying station for drying thehydro-entangled nonwoven web is arranged downstream of thehydro-entangling station.
 3. A plant according to claim 2 wherein thedrying station is adapted to act upon the hydro-entangled nonwoven webwith temperature sufficient to further bond the synthetic fibres.
 4. Aplant according to claim 2 wherein the drying station comprises arotatable drum which has a perforated wall for during operationsupporting a length of the hydroentangled nonwoven web andsimultaneously allowing a stream of air to pass.
 5. A plant according toclaim 1 wherein the plant comprises at least three in successionarranged airlaying stations.
 6. A nonwoven fabric in the form of athree-layered hydro-entangled sandwich fibre web comprising at leastsynthetic fibres and cellulosic fibres produced in a plant comprising:at least one air-laying station comprising: an endless wire, a suctionbox, which is connected to a vacuum pump, said suction box being placedunder said endless wire, first, second, and third air-laying formingheads each comprising a house with one or more fibre inlets, said housebeing placed above the upper part of said endless wire,and a number ofrotatably arranged wings for during operation disbributing the fibres ina non-woven web upon the upper part of said endless wire, said wingsbeing placed above said endless wire in said house, at least onebeat-treatment station for bonding the synthetic fibres by heating theweb, said heat-treatment station being arranged downstream of said atleast one air-laying station, at least one hydro-entangling station fordirecting a number of powerful liquid jets against the bonded web, saidhydro-entangling station being arranged downstream of said at least oneheat-treatment station, and means for continuous transport of the webthrough the plant, wherein the non-woven fabric is produced by:supplying synthetic fibres to the first forming head for forming a layerof the web; supplying cellulose fibres to the second forming head forforming another layer of the web; supplying synthetic fibres to thethird forming head for forming another layer of the web; successivelylaying the layers on top of one another whereby a three-layered sandwichfibre web is formed; hydro-entangling the thus formed web for forming astrong bond between the fibres in the layers of the web; and heating theweb at the heat-treatment station for bonding the synthetic fibres anddrying the web.
 7. A nonwoven fabric according to claim 6 wherein atleast part of the synthetic fibres are bi-component fibres, which eachconsists of a core of a first plastic surrounded by a second plastichaving a higher lower melting point than the first plastic.
 8. Anonwoven fabric according to claim 6 wherein the fabric comprisescellulose fibres present in an amount of between 50% and 95%, whereinthe cellulose fibres are provided in the web by forming a separate layerof the cellulose fibres and associating the layer of cellulose fibreswith the layer of synthetic fibres prior to hydro-entangling and heatingof the web.
 9. A nonwoven fabric according to claim 6 8 wherein thefabric comprises cellulose fibres present in an amount of between 60%and 90%.
 10. A nonwoven fabric according to claim 6 8 wherein the fabriccomprises cellulose fibres present in an amount of between 75% and 85%.11. A nonwoven fabric according to claim 6 wherein the three-layeredhydro-entangled sandwich fibre web comprises top, bottom and middlelayers, with the top and bottom layers comprising the synthetic fibresand the middle layer comprising the cellulose fibres.
 12. A plantaccording to claim 1, wherein the plant is used for production of athree-layered sandwich-fibre web.
 13. A process for forming athree-layered hydro-entangled sandwich fibre web, said processcomprising: supplying to a first air-laying forming head fibres for thebottom layer, said fibres comprising at least synthetic fibres;supplying to a second air-laying forming head fibres for the middlelayer, said fibres comprising at least cellulose fibres; supplying to athird air-laying forming head fibres for the top layer, said fibrescomprising at least synthetic fibres; forming the three layers in theeach layer's separate forming head; successively laying the layers ontop of one another whereby a three-layered sandwich fibre web is formed;hydro-entangling the thus formed web for forming a strong bond betweenthe fibres in the web; and heating the web for bonding the syntheticfibres and drying the web.
 14. A nonwoven fabric comprising thethree-layered hydro-entangled sandwich fibre web produced by the processof claim
 13. 15. A nonwoven fabric according to claim 14 wherein the webcomprises at least synthetic fibres and cellulosic fibres wherein atleast part of the synthetic fibres are bi-component fibres, which eachconsists of a core of a first plastic surrounded by a second plastichaving a lower melting point than the first plastic.
 16. A nonwovenfabric according to claim 15 wherein the fabric comprises cellulosefibres present in an amount of between 50% and 95%, wherein thecellulose fibres are provided in the web by forming a separate layer ofthe cellulose fibres and associating the layer of cellulose fibres withthe layer of synthetic fibres prior to hydro-entangling and heating ofthe web.